Celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m., Mole Day commemorates "Avogadro's Number": 6.02 x 10 23. This number--called a mole--is a basic measuring unit in chemistry. Mole Day ...

World Post Day is celebrated each year on 9 October, the anniversary of the establishment of the Universal Postal Union in 1874 in the Swiss Capital, Bern. It was declared World Post Day by the ...